The invention relates to the general field of micro-chemistry with particular reference to polymerase chain reactions.
Existing miniaturized thermal cyclers, for controlled chemical reactions in general and for polymerase-chain-reaction (PCR) in particular, are usually expensive or non-disposable due to expensive materials and high manufacturing costs (e.g. silicon/glass) for large size chips (usually  greater than 100 mm2). Low-cost plastic chips have been developed for multi-chamber reactions, but these offer only a single thermal protocol. Multi-chamber independent thermal multiplexing has many advantages to offer (e.g. for rapid PCR parallel processing) but is still not yet available in the micro-world.
Miniaturized thermal cyclers have been successfully demonstrated for years in the application of the amplification of nucleic acids with the well-known polymerase chain reaction (PCR) technology [1-8]. Quick and accurate thermal cycling can be easily achieved in very small sample volume consumption in a micro thermal cycler. Most of the recently developed microthermal cyclers are fabricated using microelectronic techniques which are popularly used in the integrated circuit (IC) industry and micro-electromechanical systems (MEMS) applications. Due to the expensive materials and processing, such a miniaturized thermal cycler usually costs quite a number of dollars/chip, a far cry from a disposable chip which is usually required in many biomedical and other biotechnology applications.
To achieve a disposable biochip, e.g., PCR thermal cycler, plastics have been investigated by several groups. Bio- and temperature compatible plastics (e.g., polypropylene and polycarbonate, etc.) are popular materials used in macro-PCR thermal cyclers in a format of vessel/tube. Although plastics themselves show fair thermal conductivity compared with silicon and glass, which might result in slow thermal response and bad temperature uniformity, its low cost, in materials and processing (mold replication), makes it promising for mass production of disposable PCR chips, especially when a large chip is required for a definite volume (e.g.  greater than 1-10 xcexcL).
A multi-chamber thermal cycler using the same thermal protocol has been developed by Baier [8]. To further take advantage of the multi-chamber, we have developed a multi-chamber thermal cycler where each chamber can be independently controlled by an individual thermal protocol. This makes it possible to simultaneously run a large number of PCR amplifications having different thermal protocols in a short time, which is very useful and important in optimization of mass PCR protocols, and in multi-PCR parallel multiplexing using individually controllable thermal cycling
Multi-chamber independent thermal cyclers can be presently seen in the macro world only in Cepheid""s products (4 chambers in 1997 and 16 chambers in 2000).
The present invention teaches how to build up a miniaturized multi-chamber (at least 1-chamber) thermal cycler for independent thermal multiplexing at relatively low-cost or a disposable micro-PCR or xcexc-thermal cycling related reaction chips.
The reference numbers used above refer to the following:
1. M. Allen Northrop, et al, (Lawrence Livermore National Lab, UC Berkeley, Roche Molecular Systems), xe2x80x9cDNA Amplification with a microfabricated reaction chamberxe2x80x9d, 7th Intl. Conf. Solid-state sensors and actuators pp. 924-926.
2. Adam T. Woolley, et al, (UC Berkeley), xe2x80x9cFunctional Integration of PCR Amplification and Capillary Electrophoresis in a Microfabricated DNA Analysis Devicexe2x80x9d, Analytical Chemistry, Vol. 68, pp. 4081-4086.
3. S- Poser, et al, xe2x80x9cChip Elements for Fast Thermocyclingxe2x80x9d, Eurosensors X, Leuven, Belgium, Sep 96, pp. 1197-1199.
4. Ajit M. Chaudhari, et al, (Stanford Univ. and PE Applied Biosystems), xe2x80x9cTransient Liquid. Crystal Thermometry of Microfabricated PCR Vessel Arraysxe2x80x9d, J. Micro-electromech. Systems, Vol, 7, No. 4, 1998, pp. 345-355.
5. Baier Volker, et al, (Jena Germany), xe2x80x9cMiniaturized multi-chamber thermocyclerxe2x80x9d, U.S. Pat. No. 5,939,312, Aug. 17, 1999.
6. Northrup; M. Allen, (Berkeley, Calif.), xe2x80x9cMicrofabricated reactorxe2x80x9d, U.S. Pat. No. 5,639,423, Jul. 17, 1997.
7. Northrop; M. Allen, (Berkeley, Calif.), xe2x80x9cMicrofabricated reactorxe2x80x9d, U.S. Pat. No. 5,646,039, Jul. 8, 1997.
8. Northrop; M Allen, (Berkeley, Calif.), xe2x80x9cMicrofabricated reactorxe2x80x9d, U.S. Pat. No. 5,674,742, Oct. 7, 1997.
It has been an object of the present invention to develop a thermal cycler for multi-chamber independent thermal control, using low-cost reusable or disposable miniaturized reaction chips.
Another object has been to provide a process to manufacture said thermal cycler.
These objects have been achieved by means of an apparatus made up of a chip of plastic, or similar low cost material, containing an array of reaction chambers. After all chambers have been filled with reagents, the chip is pressed up against a substrate, typically a printed circuit board, there being a set of temperature balancing blocks between the chip and the substrate. Individually controlled heaters and sensors located between the blocks and the substrate allow each chamber to follow its own individual thermal protocol while being well thermally isolated from all other chambers and the substrate. The latter rests on a large heat sink to avoid thermal drift over time. A process for manufacturing the apparatus is also disclosed.